The present invention relates generally to data storage systems. More particularly, the invention is directed to a data storage system that includes a local data storage facility that is mirrored by a geographically remote backup data storage facility.
In today""s commercial environment, maintaining some form of backup of data is no longer a luxury, but a necessity. A company""s financial health so relies upon the data it keeps that loss, corruption, or theft of that data can be economically disastrous. To protect against such loss, a number of data storage solutions have been considered.
Many of those solutions rely upon transfer of the data, on a periodic basis, from the main data storage facility to some form of storage medium for protective custody elsewhere. This xe2x80x9celsewherexe2x80x9d may be in the same general locale (e.g., same floor of a building, or somewhere in the same office complex) as the original data. This approach provides a backup should the main storage facility fail or the data is severely corrupted. However, the approach assumes the risk of data loss, both original and backup, in the face of truly disastrous events such as fires, floods, or earthquakes. Accordingly, many businesses eschew this approach in favor of locating a backup storage facility geographically remote from the main storage facility, for example in another city or state. This latter approach allows recovery from catastrophic events that may destroy the main storage facility yet not touch the remote storage facility by keeping a copy of the data created and maintained at the main storage facility at the remote storage facility.
xe2x80x9cRemote copyxe2x80x9d is one of the technologies presently being used for replicating data at a remote storage facility. When employed, this technology will perform a data transfer from the main or local storage facility to the remote storage facility each time data is written and/or updated to a storage device of the local facility. However, even this approach has problems. Many implementations of remote copy technologies use a wide area network, such as the Internet as the medium for transferring data from the local storage facility to the remote storage facility. When large amounts of data is being transferred, the transfer speed can result in data loss should a catastrophic event occur before or during the remote cop operation of data transfer to the remote storage facility. This is not such an infrequent possibility, because in many instances the update must wait for the availability of the network at the local storage facility, lengthening the window for data loss from a catastrophic event.
It should be evident that the risk of losing data should be minimized.
The present invention is a method, and apparatus for implementing that method, of performing a remote copy transfer of data from a local storage facility to a geographically remote storage facility on a prioritized basis. Data is assigned a priority at the local storage facility based upon the importance of that data. Some data will have a high priority, other data a lower priority. Data is transferred according to the assigned priorities.
Broadly, the present invention is directed to a data processing system having a main or local storage facility for storing data and at least one geographically remote storage facility that mirrors the data stored at the local storage facility. Generally, data is stored at the local storage facility in predefined xe2x80x9cstorage areas,xe2x80x9d which may be disk storage devices, files (for those storage systems using file-level I/O), or blocks (for storage systems using block-level I/O). Maintained at the local storage facility is a pair table that identifies pairs of storage areas, one of the pair being a storage area of the local storage facility and the other being a corresponding storage area of the remote storage facility. Associated with each of the pairs is an assigned priority.
Changes to the data, prompted by write requests received by the local storage facility, will initiate a remote copy operation that results in a transmission of the changed data to the remote storage facility. A remote copy request, identifying the data to be transferred, and the corresponding pair of storage areas affected, is created and queued. Periodically, the queue is reviewed, and thost remote copy requests associated with storage areas with an assigned higher priority are transmitted first, followed by data written to a storage areas assigned a lower priority.
A number of advantages should be evident from the present invention. First, critical data is backed up at the remote storage site as quickly as possible. No longer will such data risk loss by waiting for transmission of less critical data.
These and other aspects and advantages of the present invention will become apparent to those skilled in this art upon reading of the following detailed description of the invention, which should be taken in conjunction with the accompanying drawings.